Table Of Contents
Scatter¶
Scatter is used to build interactive widgets that can be translated, rotated and scaled with two or more fingers on a multitouch system.
Scatter has its own matrix transformation: the modelview matrix is changed before the children are drawn and the previous matrix is restored when the drawing is finished. That makes it possible to perform rotation, scaling and translation over the entire children tree without changing any widget properties.
That specific behavior makes the scatter unique, but there are some advantages / constraints that you should consider:
- The children are positioned relative to the scatter similar to a RelativeLayout (see relativelayout). So when dragging the scatter, the position of the children don’t change, only the position of the scatter.
- The scatter size has no impact on the size of the children.
- If you want to resize the scatter, use scale, not size. (read #2.). Scale transforms both the scatter and its children, but does not change size.
- The scatter is not a layout. You must manage the size of the children yourself.
For touch events, the scatter converts from the parent matrix to the scatter matrix automatically in on_touch_down/move/up events. If you are doing things manually, you will need to use to_parent() and to_local().
Usage¶
By default, the widget does not have a graphical representation. It is a container only. The idea is to combine Scatter with another widget, for example Image:
scatter = Scatter()
image = Image(source='sun.jpg')
scatter.add_widget(image)
Control Interactions¶
By default, all interactions are enabled. You can selectively disable them using the do_{rotation, translation, scale} properties.
Disable rotation:
scatter = Scatter(do_rotation=False)
Allow only translation:
scatter = Scatter(do_rotation=False, do_scale=False)
Allow only translation on x axis:
scatter = Scatter(do_rotation=False, do_scale=False,
do_translation_y=False)
Automatic Bring to Front¶
If the Scatter.auto_bring_to_front property is True, the scatter widget will be removed and re-added to the parent when it is touched (brought to front, above all other widgets in the parent). This is useful when you are manipulating several scatter widgets and don’t want the active one to be partially hidden.
Scale Limitation¶
We are using a 32-bit matrix in double representation. That means we have a limit for scaling. You cannot do infinite scaling down/up with our implementation. Generally, you don’t hit the minimum scale (because you don’t see it on the screen), but the maximum scale is 9.99506983235e+19 (2^66).
You can also limit the minimum and maximum scale allowed:
scatter = Scatter(scale_min=.5, scale_max=3.)
Behaviors¶
Changed in version 1.1.0: If no control interactions are enabled, then the touch handler will never return True.
- class kivy.uix.scatter.Scatter(**kwargs)[source]¶
Bases: kivy.uix.widget.Widget
Scatter class. See module documentation for more information.
Events: - on_transform_with_touch:
Fired when the scatter has been transformed by user touch or multitouch, such as panning or zooming.
Changed in version 1.8.0: Event on_transform_with_touch added.
- apply_transform(trans, post_multiply=False, anchor=(0, 0))[source]¶
Transforms the scatter by trans (on top of its current transformation state).
Parameters: - trans: transformation matrix from transformation lib.
Transformation to be applied to the scatter widget.
- anchor: tuple, defaults to (0, 0).
The point to use as the origin of the transformation (uses local widget space).
- post_multiply: bool, defaults to False.
If True, the transform matrix is post multiplied (as if applied before the current transform).
- auto_bring_to_front¶
If True, the widget will be automatically pushed on the top of parent widget list for drawing.
auto_bring_to_front is a BooleanProperty and defaults to True.
- bbox¶
Bounding box of the widget in parent space:
((x, y), (w, h)) # x, y = lower left corner
bbox is an AliasProperty.
- do_collide_after_children¶
If True, the collision detection for limiting the touch inside the scatter will be done after dispaching the touch to the children. You can put children outside the bounding box of the scatter and still be able to touch them.
New in version 1.3.0.
- do_rotation¶
Allow rotation.
do_rotation is a BooleanProperty and defaults to True.
- do_scale¶
Allow scaling.
do_scale is a BooleanProperty and defaults to True.
- do_translation¶
Allow translation on the X or Y axis.
do_translation is an AliasProperty of (do_translation_x + do_translation_y)
- do_translation_x¶
Allow translation on the X axis.
do_translation_x is a BooleanProperty and defaults to True.
- do_translation_y¶
Allow translation on Y axis.
do_translation_y is a BooleanProperty and defaults to True.
- on_transform_with_touch(touch)[source]¶
Called when a touch event has transformed the scatter widget. By default this does nothing, but can be overriden by derived classes that need to react to transformations caused by user input.
Parameters: touch: the touch object which triggered the transformation. New in version 1.8.0.
- rotation¶
Rotation value of the scatter.
rotation is an AliasProperty.
- scale¶
Scale value of the scatter.
scale is an AliasProperty.
- scale_max¶
Maximum scaling factor allowed.
scale_max is a NumericProperty and defaults to 1e20.
- scale_min¶
Minimum scaling factor allowed.
scale_min is a NumericProperty and defaults to 0.01.
- transform¶
Transformation matrix.
transform is an ObjectProperty and defaults to the identity matrix.
- transform_inv¶
Inverse of the transformation matrix.
transform_inv is an ObjectProperty and defaults to the identity matrix.
- translation_touches¶
Determine whether translation is triggered by a single or multiple touches. This only has effect when do_translation = True.
translation_touches is a NumericProperty and defaults to 1.
New in version 1.7.0.
- class kivy.uix.scatter.ScatterPlane(**kwargs)[source]¶
Bases: kivy.uix.scatter.Scatter
This is essentially an unbounded Scatter widget: it’s a convenience class to make it easier to handle infinite planes.